Digital Modulation Techniques

Fundamental to all wireless communications is modulation, the process of impressing the data to be transmitted on the radio carrier. Most wireless transmissions today are digital, and with the limited spectrum available, the type of modulation is more critical than it has ever been. The main goal of todays era is to squeeze modulation data as much  into the least amount of spectrum possible. That objective, known as spectral efficiency, measures how quickly data can be transmitted in an assigned bandwidth. The unit of measurement is bits per second per Hz (b/s/Hz). Multiple techniques have emerged to achieve and improve spectral efficiency. Digital Signals: are signals with amplitudes that may take only a specific number of values. Modulation: is changing one or more of the characteristics of a signal (known as the carrier signal) based on the value of another signal (known as the information or modulating signal) to produce a modulated signal.  Amplitude Shift Keying (ASK) ...